WASHINGTON – A conservation group on Thursday sued the Trump administration for withholding documents related to its decision to cancel a 20-year ban on mining in a Minnesota wilderness area and open it up to copper production.

The Wilderness Society filed the lawsuit in a Washington, DC, federal court to force the Trump administration to respond to two dozen Freedom of Information Act (FOIA) requests for documents detailing its decision to open up the Boundary Waters Canoe Area Wilderness to sulfide ore copper mining.

The group requested FOIA records last September from the Department of Agriculture, US Forest Service, Department of the Interior and Bureau of Land Management but received no response.

USDA Secretary Sonny Perdue announced last September that the Forest Service would cancel the ban on mining in the area and terminated the environmental impact study on mining on the Boundary Waters.

"We believe that the documents in question will confirm what we all know, which is that the science and public opinion definitively show that copper mining poses an unacceptable risk to this iconic wilderness area," said Allison Flint, a lawyer for the Wilderness Society.

Last month, the BLM granted hard rock mineral leases in the wilderness area to Twin Metals Minnesota, a subsidiary of Chile's Antofagasta.

Conservation and local groups, as well as some Minnesota lawmakers, have for years opposed the idea of opening up the area near the Boundary Waters to mining because of the environmental risk it poses to the area's gray wolves, black bears, and moose and a variety of fish.

The Canadian government also raised concerns about the impact mining could have on Canada's water quality and ecosystems, since the leases would be in shared US and Canadian watersheds, during the comment period on the environmental assessment.

Maya Kane, an attorney representing the Wilderness Society, said the agencies failed to comply with FOIA's statutory mandates by withholding documents, which limits public access to information about the environmental impact of opening up the popular wilderness area.

Twin Metals CEO Kelly Osborne had said the Trump decision to open up the area for mining was "very good news for us and for the communities in northeastern Minnesota who look forward to the hundreds of jobs and major economic development this mine will bring."